Rovnoleptochromus, Jałoszyński, Paweł & Perkovsky, Evgeny, 2016

Jałoszyński, Paweł & Perkovsky, Evgeny, 2016, Diversity of Scydmaeninae (Coleoptera: Staphylinidae) in Upper Eocene Rovno amber, Zootaxa 4157 (1), pp. 1-85 : 10-15

† Rovnoleptochromus gen. n.

Type species: Rovnoleptochromus ableptonoides (here designated).

Diagnosis. A genus of Clidicini with postgenae bearing long bristles but lacking cuticular postgenal processes; vertex lacking posterolateral bristles; maxillary palpomere II lacking cuticular projection but bearing one long bristle; maxillary palpomere III 3 × as long as broad, with strongly oblique apex; maxillary palpomere IV subtriangular, broadest at base; pedicel distinctly longer than antennomere III; mesoventral intercoxal process narrowly subtriangular and pointed posteriorly; mesocoxal cavities carinate posteriorly; metaventrite with median longitudinal carina; abdominal sternite III (i.e., the first visible sternite) with broadly inversely V-shaped anterior transverse carina.

Description. Body ( Figs 39–42 , 44–45 , 47–48 ) strongly elongate and flattened, with distinctly marked constrictions between head and pronotum and between pronotum and elytra, BL about 2 mm.

Head capsule ( Figs 39, 43 , 44–46, 48 ) with anterior part (in front of occipital constriction) transverse; eyes located anteriorly, large, strongly convex, oval and finely faceted; occipital constriction much narrower than vertex just behind eyes; vertex lacking posterolateral bristles; mouthparts only partly visible, labrum ( Fig. 48 ; lbr) transverse and anteriorly emarginated; mandibles ( Fig. 46 ; md) each with at least two preapical mesal teeth. Maxillary palps longer than head and slender, each composed of small, elongate palpomere I ( Fig. 46 ; mxp1); evenly curved palpomere II ( Fig. 46 ; mxp2) which is about 4.5 × as long as broad, gradually and moderately broadening distally, bearing one long bristle in proximal third of dorsal margin; strongly elongate palpomere III ( Fig. 46 ; mxp3) 3 × as long as broad, strongly and gradually broadening distally and with strongly oblique apical margin; and short, subtriangular palpomere IV ( Fig. 46 ; mxp4; the shape of palpomeres III and IV is visible in the left palp, which is shown with palpomeres III and IV in strictly ventral view), about twice as long as broad, broadest at base. Constriction between maxillary palpomeres III and IV weakly marked. Labial palps ( Fig. 46 ; lp) with large and elongate palpomere II and small, elongate and pointed palpomere III. Posterior tentorial pits ( Fig. 46 ; ptp) elongate and well-visible, each connected with outer margin of postcardinal region by hypomeral ridge ( Fig. 46 ; hr). Each postgena with two long postgenal bristles ( Fig. 46 ; pgb), lacking postgenal process.

Antennae ( Figs 39–46, 48 ) long and slender, slightly shorter than half BL, scape ( Fig. 48 ; an1) about 5–6 × as long as broad, nearly straight, distinctly but weakly broadening distally, with deep apical notch; pedicel ( Fig. 48 ; an2) much narrower and shorter than scape, slightly broadened distally, distinctly longer than antennomere III; flagellomeres (i.e., antennomeres III–XI) gradually broadening, each except XI broadest distally to middle, antennomere XI suboval, symmetrical.

Pronotum ( Figs 39–41, 43 , 46, 47 ) in dorsal view ( Fig. 47 ) strongly elongate and broadest near anterior fifth, convex, with short posterior pronotal collar ( Fig. 47 ; pnc) distinctly demarcated from disc by transverse row of several (at least four, poorly visible in specimen) large antebasal pits or impressions ( Fig. 47 ; abp).

Ventral structures of prothorax ( Figs 42 , 48 ) poorly visible; basisternal part of prosternum seems moderately long, procoxae contiguous; shape of mesal margins of prothoracic hypomera indicate open procoxal sockets.

Mesonotum only partly and poorly visible ( Fig. 47 ); mesoscutellum ( Fig. 47 ; scl3) elongate.

Mesoventrite ( Fig. 48 ) with carinate, very narrow and subtriangular mesoventral intercoxal process ( Fig. 48 ; msvp), distinctly narrowing posteriorly and with pointed apex.

Metaventrite ( Figs 42 , 45 , 48 ) subrectangular with sides rounded and in posterior fourth narrowing; posterior margins of mesocoxal cavities with carinae ( Fig. 48 ; pcmc); posterior margin of ventrite deeply concave in admetacoxal regions and forming very short and broad metaventral intercoxal process ( Fig. 48 ; mtvp) between metacoxae, with weakly concave posterior margin. Metaventrite with narrow but distinct median longitudinal carina ( Fig. 48 ; mvc) extending from mesoventral intercoxal process to near posterior margin of ventrite. Metanepisterna ( Fig. 45 ; aest3) broadening posteriorly, partly visible in ventral view ( Fig. 48 ); metepimera ( Fig. 45 ; epm3) narrow, nearly parallel-sided and visible in lateral view.

Elytra ( Figs 39–41 , 44–45 , 47 ) strongly elongate and flattened; humeral calli weakly marked, lateral elytral margins nearly parallel in anterior half; elytral apices rounded; each elytron with five impressed rows of large pits visible in dorsal view ( Fig. 47 ), striae reducing in depth in posterior fourth of elytra.

Hind wings ( Fig. 45 ; hw) present and protruding from under elytra.

Legs ( Figs 39–40, 42 , 44–45 , 48 ) long and slender; pro- and mesocoxae subconical, metacoxae with weakly transverse proximal portion and subconical distal part; all trochanters short and subtriangular, protrochanter with weakly visible distal bristles; femora gradually clavate, profemora lacking ventral bristles; tibiae long and slender, weakly curved or nearly straight; tarsi slender and long, all tarsomeres elongate and subcylindrical.

Abdomen ( Fig. 48 ) covered by elytra, six sternites visible in ventral view ( Fig. 48 ; st3–8); sternite III distinctly longer than IV, with broadly and inversely V-shaped anterior transverse carina ( Fig. 48 ; vc); suture between sternites VII and VIII distinct.

Distribution and composition. Rovnoleptochromus is represented by only one species, R. ableptonoides , described below and known from the Late Eocene of Europe ( Fig. 38 ), area currently within north-western Ukraine.

Etymology. Rovnoleptochromus is derived from the genus name Leptochromus and the geographic name Rovno. Gender masculine.

Remarks. Mastigitae are most likely a paraphyletic group in relation to Scydmaenini of Scydmaenitae ( Jałoszyński 2012c, 2014b); beetles currently classified in these taxa share the geniculate antennae (the apex of the scape is notched, so that the antennae can bend between the scape and pedicel), the prosternum laterally fused with prothoracic hypomera, and the metacoxae broadly separated. Scydmaenini , as currently defined, can be easily distinguished from all species of Mastigitae on the basis of the maxillary palpomere IV, which is short, domeshaped and symmetrical, and its base is clearly narrower than the apex of palpomere III. In Mastigitae, palpomere IV is either large, elongate subtriangular or suboval (Mastigini and Clidicini), or short, but then strongly asymmetrical (with strongly oblique base) and at base as broad as the apex of palpomere III (Leptomastacini). Based on these characters, Rovnoleptochromus can be unambiguously recognized as a member of Mastigitae. The structure of maxillary palps (palpomere IV elongate), the pedicel short and thin and the scape and pedicel lacking two rows of long bristles place this genus within Clidicini.

Clidicini include three extant genera, Clidicus, Laporte, 1832 , Leptochromus Motschulsky, 1855 and Papusus, Casey, 1897 , and three extinct genera, Palaeoleptochromus O'Keefe, 1997 (in O'Keefe, Pike & Poinar (1997)) in Canadian Campanian amber, Euroleptochromus Jałoszyński, 2012a in Eocene Baltic amber and Rovnoleptochromus . The systematic position of Papusus remains problematic and unsolved ( Jałoszyński 2012a, 2015); this genus, associated with unusual for Scydmaeninae arid habitats of Nearctic deserts, shows unique characters and may in future be excluded from Clidicini. Clidicus , Leptochromus , Palaeoleptochromus , Euroleptochromus and Rovnoleptochromus share the strongly elongate scape, which is more than twice as long as the pedicel, and distinct rows of punctures on the elytra. All these genera, except Clidicus , have postgenal ('subocular' of O'Keefe et al. (1997)) bristles on the head and bristles on protrochanters; Leptochromus , Palaeoleptochromus and Euroleptochromus additionally have bristles along the ventral margin of profemur. Leptochromus is defined (among other characters) by an elongate cuticular projection on the maxillary palpomere II bearing two thick bristles at apex, and a strongly elongate (at least four times as long as broad) maxillary palpomere IV, distinctly broadest in its distal half ( O'Keefe 2002). Palaeoleptochromus , Euroleptochromus and Rovnoleptochromus lack the cuticular projection of palpomere III and have the palpomere IV less elongate (less than three times as long as broad), broadest either at base or near middle. Palaeoleptochromus has the maxillary palpomere IV clearly subtriangular, broadest at base; the maxillary palpomere II evenly curved; and a pair of long bristles on the posterior margin of the vertex ( O'Keefe et al. 1997). Euroleptochromus has the maxillary palpomere IV suboval, broadening from base to middle and then narrowing distally; the maxillary palpomere II with its mesal margin with an angulate protuberance bearing a group of bristles; it lacks the pair of the posterior vertexal bristles; and has a slender and strongly elongate postgenal projection with two apical bristles ( Jałoszyński 2012a). The latter character was recently found in a newly described extant species of Leptochromus ( Lord, Carlton & Leschen 2014) , all remaining species of Leptochromus has the postgenae either unmodified or with a weakly raised angulate or tuberculate protuberance bearing the postgenal bristles ( O'Keefe 2002). The newly described Rovnoleptochromus has the maxillary palpomere IV approximately subtriangular, broadest at base (see the left palp in Fig. 46 ); the maxillary palpomere II evenly curved; and lacks the vertexal bristles and the postgenal process. Additionally, Rovnoleptochromus has the longitudinal metaventral carina, a character not known in any extant or extinct Clidicini, but present in Ablepton Frivaldszky, 1877 of Leptomastacini (Jałoszyński, unpublished obs.). Key characters of all genera of Clidicini are compiled in Table 1.

Rovnoleptochromus in a preliminary phylogenetic analysis was placed as a component of the ' Leptochromus lineage' of Clidicini, i.e., a member of a group that includes Leptochromus , Palaeoleptochromus and Euroleptochromus , and as a sister group to a clade composed of these three genera (Jałoszyński, unpublished results).

Clidicus Papusus Leptochromus † Palaeoleptochromus † Euroleptochromus † Rovnoleptochromus

Cuticular projection absent absent long anđ bearing two absent tuberculate, weakly absent

maxillary apical bristles raiseđ, with 2-3 bristles

palpomere II

Maxillary palpomere 2$3 × as long as broađ, at least 4 ×as long as at least 4 × as long as about 3 × as long as> 5 × as long as broađ, 3 × as long as broađ, with oblique apical broađ, with transverse broađ, with nearly broađ, with oblique with transverse apical with oblique apical margin apical margin transverse apical apical margin margin margin margin

Maxillary palpomere subtriangular, broađest subtriangular, broađest suboval, broađest in subtriangular, broađest suboval, broađest near subtriangular, broađest at base, 2$3 × as long at base, about 2 × as đistal half, at least 4 × at base, about 2 × as miđđle, 2.5 × as long at base, about 2 × as as broađ long as broađ as long as broađ long as broađ as broađ long as broađ

Posterolateral absent absent absent present absent absent

vertexal setae

Postgenal process absent absent absent or present, from absent rođ-like absent weakly raiseđ tubercle

to slenđer rođ

Poastgenal absent absent present present present present

subocular) bristles

Posterior margins of carinate carinate non-carinate unknown carinate carinate

mesocoxal cavities

Mesoventral parallel-siđeđ or parallel-siđeđ parallel-siđeđ unknown parallel-siđeđ narrowing posteriorly

intercoxal process slightly broađening

posteriorly

Elytral striae đistinct inđistinct or absent đistinct đistinct đistinct đistinct

Međian longituđinal absent absent absent unknown absent present

metaventral carina

Protrochanteral absent absent present present present present

bristles

Profemoral bristles absent absent present present present absent

Figures

FIGURES 39 – 43. Holotype of Rovnoleptochromus ableptonoides sp. n. (K- 27418). Laterodorsal (39), lateral (40), dorsal (41) and ventral (42) view of whole specimen; anterior portion of body showing head in ventrolateral view (43).

FIGURES 44 – 45. Holotype of Rovnoleptochromus ableptonoides sp. n. (K- 27418). Laterodorsal (44) and lateral 45) view. Abbreviations: aest 3, metanepisternum; epm 3, metepimeron; hw, hind wing; mcp, mesocoxal projection; pcxb, procoxal bristles; pgb; postgenal bristles; pre, prepectus.

FIGURES 46 – 48. Holotype of Rovnoleptochromus ableptonoides sp. n. (K- 27418). Head in ventrolateral view (46), pronotum and elytra in dorsal view (47), body in ventral view (48). Abbreviations: abp, antebasal pit; aest 3, metanepisternum; an 1 − 11, antennomere I − XI; fr, frons; hr, hypostomal ridge; lbr, labrum; lp 2 − 3, labial palpomere II − III; md, mandible; mn, mentum; msvp, mesoventral process; mtvp, metaventral process; mvc, metaventral carina; mxp 1 − 4, maxillary palpomere I − IV; pcmc, posterior carina of mesocoxal cavity; pgb, postgenal bristles; pn, pronotum; pnc, pronotal collar; ptp, posterior tentorial pit; slc 2, mesoscutellum; smn, submentum; st 3 − 8; abdominal sternite III − VIII; v 3, metaventrite; vc, V-shaped carina.

FIGURES 35 – 38. Location of the Rovno Region (35 − 36) and the Klesov, Dubrovitsa and Vyrka amber mines (37) in the present-day Europe; location of the Rovno Region during Eocene (38).